A conventional power stapler includes two functions one of which is single shoot and the other is continuous shoot. It is dangerous if the single shoot and the continuous shoot cannot be controlled with care. If the user thought it is a single shoot function, however, the staples shoot continuously then people could be injured by the powerful staples. Generally, the user has to push a safety member before each shoot so as to effectively let the stapler be injected from the power stapler. After a single shoot, if the pressing member connected to the trigger member is not firmly positioned at the expected position then, under some particular situations, the trigger could be unintentionally pulled again and the pressing member could push the valve rod again to shoot another staple.
The present invention intends to provide a trigger assembly which ensures the pressing member will not return to its original position after shooting except the safety member is removed from the pressing member. By this trigger assembly of the present invention, the single shoot will never be mis-activated.